Urinary incontinence is a condition in which involuntary leakage of urine is involved and recognized objectively and these become social or hygienic problems (Non-Patent Document 1). As typical examples of the urinary incontinence, urge urinary incontinence, stress urinary incontinence, and a mixed type of urinary incontinence which involves them have been known.
The most common type of the urinary incontinence is stress urinary incontinence and it has been reported that 50% of women suffering from the urinary incontinence is stress urinary incontinence (Non-Patent Document 2). The stress urinary incontinence refers to a disease in which when abdominal pressure rises during coughing, sneezing, exercise, or the like, urine leaks out involuntarily even though there is no contraction of the bladder. The causes of stress urinary incontinence can be largely divided into two types. One is the bladder neck/urethra hypermobility, in which the transmission of abdominal pressure to the urethra fails due to bladder neck ptosis, based on the pelvic floor muscle relaxation, and thus only the intravesical pressure rises during the rise of abdominal pressure and urine leaks. The other is that the reduction of a sphincter muscle function due to intrinsic sphincter deficiency causes urine leakage when the abdominal pressure rises. There is a high possibility that the onset of stress urinary incontinence involves weakening of the pelvic floor muscles due to aging and childbirth, and deterioration of the urethral function. In particular, the trauma of the pelvis by pregnancy and vaginal childbirth is known as a risk factor for a persistent stress urinary incontinence onset, and it has been reported that a prevalence rate of stress urinary incontinence for five years after the first birth is about 30% (Non-Patent Document 3).
Urge urinary incontinence is a disease in which urine leaks involuntarily immediately after a complaint of a strong suddenly occurring and irrepressible desire to urinate which is hard to endure (urge and sudden desire of urination). The mixed type of urinary incontinence is a condition in which a combination of plural types of urinary incontinence is developed, and most of them involves development of urge urinary incontinence and stress urinary incontinence.
Urinary incontinence has a major impact on the quality of life (QOL). Concerns about its symptoms restrict the range of activities of patients, making the patients feel loneliness and social isolation.
As a therapeutic drug for stress urinary incontinence, duloxetine having a serotonin-norepinephrine reuptake inhibitory action (SNRI) and nisoxetine having a selective norepinephrine reuptake inhibitory action (NRI) have been reported (Non-Patent Documents 4 and 5).
However, duloxetine has been reported to be effective against stress urinary incontinence in clinical trials, but has also been reported to have side effects such as nausea, insomnia, dizziness, and suicidal tendencies.
In the neuroreflex of the autonomic nerves by stretch stimulus of the bladder in the urine storage phase, an α1 adrenoceptor is present in the urethra and plays a role to maintain continence by inducing urethral contraction. To date, it has been reported that a plurality of drugs having α1 adrenoceptor agonistic actions have a strong urethral contraction action, and in clinical trials, a drug having an α1 adrenoceptor agonistic action is effective against stress urinary incontinence (Non-Patent Documents 1, 4, 6, and 7). However, it has been known that an α1 adrenoceptor agonist has cardiovascular side effects such as increased blood pressure or the like.
As described above, it is considered that as a drug treatment for stress urinary incontinence, it is effective to increase the urethral resistance so as to maintain continence when the intravesical pressure rises during the urine storage phase, and thus, drugs based on some mechanisms of action have been studied. However, there is a strong desire for development of an agent for treating stress urinary incontinence, based on a novel mechanism of action with fewer side effects.
Meanwhile, melatonin represented by the following formula is a hormone secreted by the pineal, which shows an inhibitory effect on the function and growth of gonad. Melatonin affects the circadian rhythm in animals, and plays a role to tune the reproductive function to a light cycle of the environment.

As the receptors of melatonin, there have been known three subtypes, MT1(Me11a), MT2(Me11b), and MT3(Me11c) (Non-Patent Documents 8 and 9). MT1 and MT2 are G protein-coupled receptors (GPCR) which are coupled to Gi and Gq, but MT3 is a quinone reductase (QR2) which has a melatonin binding site. The affinity of melatonin for the MT1 and MT2 receptors is high, but the affinity of melatonin for the MT3 receptor is low (Non-Patent Document 9).
Incidentally, there have been a number of reports that MT1 and/or MT2 receptor agonists are useful for the treatment of central nervous system diseases such as sleep disorders and depression.
As the representative MT1 and/or MT2 receptor agonists, a compound represented by the following formula (A) has an MT1 and MT2 receptor agonistic activity and can be used for prevention or treatment of sleep-awake rhythm disorders, jet lag, abnormality of physical condition due to work in three shifts or the like, seasonal depression disease, reproductive and neuroendocrine diseases, senile dementia, Alzheimer's disease, various disorder due to aging, cerebral circulatory disorder, head injury, spinal cord injury, stress, epilepsy, convulsions, anxiety, depression, Parkinson's disease, hypertension, glaucoma, cancer, insomnia, diabetes mellitus, and the like. The compound has been reported to be useful for modulating immunomodulation, intelligence, tranquilizers, and ovulation control (Patent Document 1). In particular, Ramelteon represented by the following formula has been known as an agent for treating insomnia characterized by hypnagogic disorder (Non-Patent Documents 10 and 11).

(Refer to this publication for the symbols in the formula.)
Moreover, it has been described that a compound represented by the following formula (B) has an MT1 and MT2 receptor agonistic activity, has many effects on the central nervous system, has particularly properties of calming, solving anxiety, antipsychotic, and analgesic, and is further useful in treatment of stress, dyssomnia, anxiety, seasonal depression, insomnia and fatigue due to jet lag, schizophrenia, panic attacks, depression, appetite adjustment, insomnia, psychotic symptoms, epilepsy, Parkinson's disease, senile dementia, and various disorders caused by common or pathological aging, migraine, memory loss, Alzheimer's disease, and blood circulation in the brain (Patent Document 2).

(Refer to this publication for the symbols in the formula.)
Furthermore, it has been described that a compound represented by the following formula (C) has an affinity for a melatonin receptor and is useful for the treatment of sleep disorders, periodic depression, deflection of a circadian cycle, melancholia, stress, appetite adjustment, benign prostatic hyperplasia, and the relevant conditions (Patent Document 3).

(Refer to this publication for the symbols in the formula.)
In addition, it has been described that a compound of the following formula (D) has an affinity for MT1 and MT2 receptors, is useful for treatment of stress, sleep disorders, anxiety, seasonal affective disorder or major depression, cardiovascular pathology, digestive system pathology, insomnia and fatigue due to jet lag, schizophrenia, panic attacks, depression, appetite disorders, obesity, insomnia, mental disorders, epilepsy, diabetes mellitus, Parkinson's disease, senile dementia, various disorders caused by normal or pathological aging, migraine, memory loss, and Alzheimer's disease, is useful against cerebral circulation disorders, has anovulation and immunomodulatory characteristics, and can be used for the treatment of cancer (Patent Document 4).

(Refer to this publication for the symbols in the formula.)
In addition, it has been described that a compound represented by the following formula (E) can be used for treatment of stress, anxiety, depression, insomnia, schizophrenia, psychosis, and epilepsy, treatment of sleep disorder associated with traveling (jet lag), and diseases due to neural degeneration (modification) of the central nervous system, such as Parkinson's disease, Alzheimer's disease or the like, and treatment of cancer, and can be used in contraception drugs or analgesics. Further, it has been described that the compound of Example 2 represented by the following formula has a superior excellent sleep effect to melatonin (Patent Document 5).

(In the formula, R1 to R6 represent a hydrogen atom, CV-R11, or lower alkylamino or the like; V represents an oxygen atom or the like; R11 represents R1; at least one of R2 and R3 represents methoxy group; R4 represents a hydrogen atom; R5 represents lower alkyl group or the like; X represents N-R7 or the like; R7 represents R1 or the like; Y represents CR8 or the like; Z represents C or the like; W represents an oxygen atom or the like; R8 represents R1; n represents integers from 1 to 4.)
Moreover, it has been described that some compounds including a compound represented by the following formula (F) have an affinity for an MT1 and/or MT2 receptor (Non-Patent Document 12).

However, there is no report in any Document that MT1 and/or MT2 receptor agonists act on the urethra and are useful for the treatment of urinary incontinence and the like.